I was just there the other day so I'll give it a go.
In the local library, the book aisles (not counting the very busy children's floor) are empty. On the periphery of the room are tables and chairs which are often occupied by young Asians with laptops connected to the free wifi. At one side of the room, the many free Internet computers are occupied by young blacks and Hispanics browsing ethnic social media. The magazine section is filled with older ethnics seated in comfy chairs, reading magazines.
Upstairs, across from the children's area, ancient white people wait -- seated -- in line to receive free help with their taxes.
Some local libraries (not ours) have a huge movie DVD section which gets a lot of traffic on Friday nights and weekends. As for books - not so much.
In general, demographics of people I see using different sections of the library are similar to those already mentioned.